I live in Austria and the biggest Internet provider is A1 Telekom Austria and they use PPPoA and not PPPoE. I’ve searched through out the Internet to find some documentation on how to configure a Mikrotik router for this. I wanted to have the public IP address on the Mikrotik and not on the provider router/modem. I did not find any documentation. But as I got it working I’ll provide such a documentation now. 😉

1. The Basics

PPPoA is the abbreviation for PPP over ATM or some say PPP over AAL5 and it is used to encapsulate PPP into ATM cells to get into the Internet via ADSL connections. The more commonly used standard in this space is PPPoE (PPP over Ethernet), but which has somewhat more overhead as you need also to encapsulate the Ethernet header too.

There are now two possibilities:

The first is that the provider modem/router handles everything and you get only a private IP address behind the router, and the router masquerade the private IP addresses. This is normally the default as it works for 95% of the customers but your PC or own router does not get a public IP address. You need to use port forwarding if you want to provide services which are reachable from the Internet. And something which I specially need. You don’t get a event when you get disconnected and assigned a new IP address. A1 Telekom Austria has the bad habit to disconnect you every 8 hours … 3 times a day. As I want to have the disconnects always at the same time I need my own router to time it once a day, so it gets reseted to my desired reconnect times.

The second way it to get somehow the public IP address on the PC or router. In this case your need a provider modem/router with a PPPoA-to-PPTP-Relays. Take a look at the picture I took from the German Wikipedia(CC-BY-SA-3.0, Author Sonos):

The computer (or Mikrotik router) thinks it establishes a PPTP tunnel with the modem, but instead the modem encapsulates the packets and send them on via ATM to the provider backbone. So the computer or Miktrotik router does not need to be able to talk PPPoA it is enough if it is able to talk PPTP, the rest is handled by the modem.

2. Requirements

But of course there are some requirements:

The provider modem needs to be able to make a PPPoA-to-PPTP-Relays and which is important you need to be able to configure it, as some provider firmwares restrict that.

You need to know the username and password which is used for the ppp authentication

And for the sake of completeness – you need a Mikrotik router 😉

3. Provider modem / router

My provider gave me a Thomson Speedtouch TG585 v7 modem/router. The firmware is old (8.2.1.5) and branded but I was able to upload a new configuration via the web interface.

And as it works stable I did not see a reason to upgrade. I found in the Internet a INI file, which configured the router to PPPoA-to-PPTP-Relays mode. Three important notes:

If you search the Internet for a configuration file … look for “single user” or “single user mode” (SU), the masquerade mode is called “multi user mode” (MU)

It is also possible to configure the single user mode via telnet, there are some howto’s out there. The specific ones for Austria are of course in German.

The version numbering is quite broken. The A1 Telekom Austria branded firmwares are often higher (e.g. 8.6.9.0) than the newer generic firmwares (e.g 8.2.6.5_AA).

After configuring the router as PPPoA-to-PPTP-Relays it has the IP address 10.0.0.138/24 for my setup.

4. Mikrotik PPP configuration

So now to the Mikrotik configuration … we start with resetting the configuration with no defaults.
/system reset-configuration no-defaults=yes

Then we rename the first interface and add a transit network IP address
/interface ethernet set 0 name=ether1vlanTransitModem
/ip address add address=10.0.0.1/24 interface=ether1vlanTransitModem

Now the Internet connection is working, we just need to make it usable ….

5. Mikrotik on the way to be usable

The first thing we need is a masquerade rule that we use the correct IP address into the Internet, following does the trick.
/ip firewall nat add action=masquerade chain=srcnat out-interface=pptpDslInternet

But we want also a client to test it … so here is the configuration I use for the clients (without explanation as it is not the topic of this Howto)
/interface ethernet set 2 name=ether3vlanClients
/ip address add address=10.23.23.1/24 interface=ether3vlanClients

Thanks a lot for your tutorial! It works basically, but i cant get the mikrotik to automatically reestablish the pptp after the modem has lost sync and the ptp interface is not marked as “running” anymore by the mikrotik

Hi, can You share config .ini file? I have TG585v7 with Be firmware 8.2.7.7, I have a problem with configuration but only default mode is active but not work with my vpi/vci (0.35) VCMUX. Pleasy share .ini file for edit.